This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. After receiving an invitation to contribute, an entry has been submitted for the new Springer Encyclopedia of Biophysics. This long entry (~3000 words) is titled "Membrane Fluidity". The encyclopedia is scheduled to appear in press in 2012.